Notifications/alert work only over 3G and not over Wifi? iOS 6 on 4S -- HELP!!

Ok Guys .. Something wierd happened today to my 4S.

All my notifications/alert are coming ONLY through 3G and NOT over wifi.

To name few apps (iMessage, Twitter, ESPN ScoreCenter, Whatsapp, etc)

Up until yesterday I was able to get notifications over wifi just fine. But starting today no more notificaitons over wifi.

When I turn on my 3G and all of a sudden I get alert on my phone about iMessages, tweets, scores, etc.

To rule few things out:

1) I tried resetting my router and did forget the network thing on my phone but still having the same issue.

2) I'm able to surf on safari just fine.

3) DND is off! Never turned it on!

4) This is not due to phone losing wifi connection when locked, because I tested it. I waited after unlocked the phone and surfed on safari for few mins to see if i get any type of notification, but nothing until I go and turn on my 3G.

5) Tried the phone on different wifi network without any luck.

Anyone else having this issue? or got fix?

Thanks!